The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Communication systems typically comprise transmitters that transmit data over a communication medium and receivers that receive data transmitted by transmitters. Often, receivers receive data that may be corrupted due to noise that distorts data during transmission. Additionally, devices surrounding receivers may generate electromagnetic waves that interfere with data received by receivers. Thus, data received by receivers may not represent data transmitted by transmitters. Consequently, receivers may not accurately interpret and process received data resulting in partial or total data loss.
Referring now to FIGS. 1A-1C, a communication system 10 comprises a transmitter 12 that transmits data to a receiver 14 over a transmission medium 16. The transmission medium 16 may be wireline or wireless. The data received by the receiver 14 may be corrupted due to interference 18 encountered during transmission and/or due to interference 19 caused by electromagnetic waves generated by other devices 20 that surround the receiver 14.
Some receivers use conventional interference detection systems that are capable of detecting interference caused by waveforms of a long duration of the type shown in FIG. 1B. The conventional interference detection systems, however, may fail to detect interference caused by strong pulses of short durations of the type shown in FIG. 1C. Radar pulses are a typical example of strong pulses of short durations that may interfere with operation of receivers in wireless communication systems. Interference caused by some strong pulses of short durations may trigger false alarms. That is, receivers may mistake some strong pulses of short durations as data.
Referring now to FIGS. 2A-2B, the receiver 14 typically comprises an antenna 30 that receives an input signal, an automatic gain control (AGC) module 32 having a gain that varies based on strength of the input signal, a mixer module 33 that mixes a signal generated by a local oscillator module 33-1 with the input signal, a filter module 34 that filters an output of the mixer module 33, an analog-to-digital converter (ADC) module 36 that converts an output of the filter module 34 from analog to digital format, and a digital signal processor (DSP) module 38 that processes an output of the ADC module 36.
Additionally, the receiver 14 typically comprises a peak detector module 40 that generates a peak-detect signal when the output of the AGC module 32 crosses a predetermined threshold in response to the input signal. The predetermined threshold is generally based on characteristics such as packet size, packet length, strength of the input signal, etc. The peak detector module 40 may generate the peak-detect signal when the AGC module 32 determines that the input signal strength is greater than a relative signal strength index (RSSI).
The peak-detect signal activates the DSP module 38. The DSP module 38 generates a gain-drop signal that drops the gain of the AGC module 32 as shown in FIG. 2B. The gain of the AGC module 32 remains low for the duration of the input signal. The duration of the input signal depends on characteristics such as packet size, packet length, etc. The gain of the AGC module 32 returns to normal at the end of the input signal.
On the other hand, an interference signal may trigger a false alarm. That is, the interference signal may cause the peak detector module 40 to mistake the interference signal as true data. The peak detector module 40 may generate the peak-detect signal for the interference signal. Subsequently, the DSP module 38 may generate the gain-drop signal that will drop the gain of the AGC module 32. The gain of the AGC module 32, however, may not return to normal since the interference signal may have unknown and/or unknowable characteristics. This can degrade system performance and may cause system malfunction and/or data loss.